The present invention relates to a scroll type compressor, which supplies compressed gas to an electrode of a fuel cell.
Japanese Unexamined Patent Publication 11-257259 discloses such a scroll type compressor. The scroll type compressor includes a movable scroll member, a fixed scroll member, an inlet and outlet. The movable scroll member has a movable scroll base plate and a movable scroll spiral wall that extends from the movable scroll base plate. The fixed scroll member has a fixed scroll base plate and a fixed scroll spiral wall that extends from the fixed scroll base plate. The movable scroll spiral wall and the fixed scroll spiral wall are engaged with each other to form a compression region between the movable scroll member and the fixed scroll member. The inlet is formed on the fixed scroll spiral wall side, which is an outside of the movable scroll spiral wall, and the outlet is formed in the middle of the fixed scroll base plate therethrough. When temperature in the compression region becomes relatively high, the movable scroll spiral wall and the fixed scroll spiral wall as a whole expand respectively in radial directions of the movable scroll base plate and the fixed scroll base plate. In the scroll type compressor, on one hand, since the outer circumferential side of the fixed scroll spiral wall, which is located near the inlet, is directly cooled by intake gas, the fixed scroll spiral wall in itself is partially maintained at relatively low temperature. On the other hand, the movable scroll spiral wall in itself, which is located inside of the fixed scroll spiral wall, is maintained at relatively high temperature by heat of compression.
Therefore, an amount of deformation of the movable scroll spiral wall becomes larger than that of the fixed scroll spiral wall. For this reason, it is highly expected that an outer circumferential wall of the movable scroll spiral wall comes in contact with an inner circumferential wall of the fixed scroll spiral wall.
To prevent the contact between the movable scroll spiral wall and the fixed scroll spiral wall by avoiding the partial differential in thermal expansion, in the above prior art, thickness of at least one of the movable scroll spiral wall and the fixed scroll spiral wall, which are placed near the inlet, is reduced.
Meanwhile, in the scroll type compressor, which supplies the compressed gas to the electrode of the fuel cell, the movable scroll base plate has a relatively large diameter. Also, a plurality of cylindrical driven crankshaft receiving portions with a bottom, which has a relatively large thickness, is placed on the back surface of the movable scroll base plate. A part of the movable scroll base plate, where the driven crankshaft receiving portions are placed, has a larger rigidity than a part of the movable scroll base plate, where the driven crankshaft receiving portion is not placed.
In the part of the movable scroll base plate, which has a relatively large rigidity, the deformation of the part of the movable scroll base plate caused by the thermal expansion is restrained. In other words, in the part of the movable scroll base plate, where the driven crankshaft receiving portion is placed, the deformation of the part of the movable scroll spiral wall is restrained. In contrast, in the part of the movable scroll base plate, where the driven crankshaft receiving portion is not placed, since the deformation of the part of the movable scroll base plate, where the driven crankshaft receiving portion is placed, is restrained, the deformation of the part of the movable scroll spiral wall, where the driven crankshaft receiving portion is not-placed, is promoted. For this reason, in the part of the movable scroll base plate, where the driven crankshaft receiving portion is not placed, it is highly expected that the outer circumferential wall of the movable scroll spiral wall strongly comes in contact with the inner circumferential wall of the fixed scroll spiral wall. In this case, however, the part where the movable scroll spiral wall is deformed is not only near the inlet as described in the above prior art. Therefore, in a manner that the thickness of at least one of the parts of the movable scroll spiral wall and the fixed scroll spiral wall, which are placed near the inlet, is reduced as described in the prior art, it is difficult to prevent the movable scroll spiral wall and the fixed scroll spiral wall from strongly coming in contact with each other. Thereby, reduction of the durability caused due to the contact, increase of the sliding loss, and increase of the sound level and vibration level are concerned.
The present invention is directed to a scroll type compressor that reduces sliding loss, sound level and vibration level and that improves durability by preventing a surface of a part of a scroll spiral wall where heat deformation is relatively large due to a difference in rigidity on a scroll base plate from strongly coming in contact with an opposing surface.
The present invention has the following features. A scroll type compressor includes a fixed scroll member, a movable scroll member, a drive crank mechanism and a plurality of driven crank mechanisms. The fixed scroll member has a fixed scroll base plate and a fixed scroll spiral wall that extends from the fixed scroll base plate. The movable scroll member has a movable scroll base plate and a movable scroll spiral wall that extends from the movable scroll base plate. The movable scroll spiral wall and the fixed scroll spiral wall are engaged with each other to form a compression region between the movable scroll member and the fixed scroll member. The drive crank mechanism is placed substantially in the middle of the movable scroll base plate. The movable scroll member orbits relative to the fixed scroll member. Thereby, fluid in the compression region is compressed. A plurality of driven crank mechanisms is annularly placed on a back surface of the movable scroll base plate. Each driven crank mechanism has a driven crankshaft receiving portion. When segments are drawn from a center of the movable scroll base plate so as to come in contact with respective driven crankshaft receiving portions and intersect with an outer circumference of the movable scroll base plate on a back surface of the movable scroll member, the driven crankshaft receiving portions, which are located next to each other, sandwich two of the segments. The two segments and an arc of the outer circumference of the movable scroll base plate define a first region, where a relieving part is formed in at least a part of at least one of an outer circumferential wall of the movable scroll spiral wall and an inner circumferential wall of the fixed scroll spiral wall, which corresponds to the outer circumferential wall of the movable scroll spiral wall. The relieving part relieves heat deformation of the movable scroll spiral wall and/or the fixed scroll spiral wall.